U.S. patent application number 15/405903 was filed with the patent office on 2018-07-19 for dissolved gas sensor and system.
This patent application is currently assigned to The United State of America, as represented by the Secretary of the Department of the Interior. The applicant listed for this patent is The United State of America, as represented by the Secretary of the Department of the Interior, The United State of America, as represented by the Secretary of the Department of the Interior. Invention is credited to Karl B. Haase, Ward E. Sanford.
Application Number | 20180202984 15/405903 |
Document ID | / |
Family ID | 62838876 |
Filed Date | 2018-07-19 |
United States Patent
Application |
20180202984 |
Kind Code |
A1 |
Haase; Karl B. ; et
al. |
July 19, 2018 |
DISSOLVED GAS SENSOR AND SYSTEM
Abstract
The dissolved gas sensor system includes a dissolved gas sensor
partially located within a housing and partially extending through
the housing lid. The sensor is created by affixing a selectively
permeable membrane to a dissolved gas transducer with a waterproof
polymer. This forms a membrane cavity between the membrane,
polymer, and transducer. The membrane cavity allows the transducer
to detect whatever gas or gases can pass through the selectively
permeable membrane. These readings pass to a controller located
within the housing body that can receive and process data, and
store the data in a removable data storage for later retrieval by a
user. The controller can also regulate overall power consumption of
the system to increase the operating life of the system.
Inventors: |
Haase; Karl B.; (Herndon,
VA) ; Sanford; Ward E.; (Herndon, VA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The United State of America, as represented by the Secretary of the
Department of the Interior |
Washington |
DC |
US |
|
|
Assignee: |
The United State of America, as
represented by the Secretary of the Department of the
Interior
Washington
DC
|
Family ID: |
62838876 |
Appl. No.: |
15/405903 |
Filed: |
January 13, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N 33/0006 20130101;
G01N 33/004 20130101; G01N 21/3504 20130101; G01N 2201/0227
20130101 |
International
Class: |
G01N 33/00 20060101
G01N033/00; G01N 21/61 20060101 G01N021/61; G01N 19/00 20060101
G01N019/00 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0001] The invention described herein was made by an employee of
the United States Government and may be manufactured and used by
the Government of the United States of America for governmental
purposes without the payment of any royalties thereon or therefore.
Claims
1. A dissolved gas sensor apparatus, comprised of: a selectively
permeable membrane; a dissolved gas transducer; a waterproof
polymer affixing said selectively permeable membrane to said
dissolved gas transducer; and a membrane cavity formed between said
selectively permeable membrane, said waterproof polymer, and said
dissolved gas transducer.
2. The apparatus of claim 1, wherein said selectively permeable
membrane is a polymer membrane selected from the group consisting
of: polytetrafluoroethylene and silicone.
3. The apparatus of claim 1, wherein said selectively permeable
membrane is permeable to at least one gas of interest selected from
the group consisting of: carbon dioxide, methane, and oxygen.
4. The apparatus of claim 3, wherein said waterproof polymer is
impermeable to said gas of interest.
5. The apparatus of claim 1, wherein said waterproof polymer is
selected from the group consisting of: polyurethane cement, epoxy
cement, and butyl rubber cement.
6. The apparatus of claim 1, wherein said dissolved gas transducer
is selected from the group consisting of: ultraviolet flux
transducers and infrared transducers.
7. The apparatus of claim 1, wherein said dissolved gas transducer
is a non-dispersive infrared transducer.
8. The apparatus of claim 1, further including a calibration tube
extending between said membrane cavity and a calibration port.
9. The apparatus of claim 8, wherein said calibration port is
capped by a removable port cap.
10. The apparatus of claim 8, wherein said calibration port is
connected to a pressure transducer.
11. A dissolved gas sensor system, comprised of: a dissolved gas
sensor, comprising: a selectively permeable membrane, a dissolved
gas transducer, a waterproof polymer affixing said selectively
permeable membrane to said dissolved gas transducer, and a membrane
cavity formed between said selectively permeable membrane, said
waterproof polymer, and said dissolved gas transducer; a housing
comprising a housing lid connected to a housing body, wherein at
least part of said dissolved gas sensor extends from within said
housing and through said housing lid; and a controller located
within said housing body, wherein said controller comprises: a
processor connected to said dissolved gas sensor, to a removable
data storage, and to a power supply, a data logger connected to
said dissolved gas sensor and to said removable data storage, a
power circuit connected to said power supply.
12. The system of claim 11, wherein said controller further
includes a clock connected to said processor and said power
circuit.
13. The system of claim 11, wherein said system further includes a
flexible, waterproof housing seal located between said housing lid
and said housing body.
14. The system of claim 11, wherein said system further includes a
housing port extending through said housing body and an external
sensor extending through said housing port.
15. The system of claim 14, wherein said external sensor s selected
from the group consisting of: radiation sensors and pressure
sensors.
16. The system of claim 11, wherein said power supply is at least
one solar panel located external to said housing.
17. The system of claim 11, wherein said power supply is at least
one battery located internal to said housing.
18. The system of claim 11, wherein said system further includes a
base connected to said housing, wherein said base includes a base
weight having sufficient mass to submerge said system.
19. The system of claim 18, wherein said base further includes at
least one base anchor connected to said base by a base connector.
Description
FIELD OF INVENTION
[0002] This invention relates to the field of gas sensors and more
specifically to a dissolved carbon dioxide sensor.
BACKGROUND OF THE INVENTION
[0003] Monitoring the levels of dissolved gasses in waterways and
the atmosphere allows scientists to evaluate waterway
acidification, oxygenation, and pollution, climate change, and
other biological and meteorological conditions. In the past,
scientists placed sensors in waterways or in open atmosphere to
continuously monitor dissolved gas levels. Membranes that were
selectively permeable to the gas under study covered the sensors to
protect them from fouling, allowing the gas to diffuse into a
cavity for detection by the sensor. Cables connected the sensors to
power and data logging units to supply power and record sensed gas
levels.
[0004] The required physical connection to a central data logger
makes distribution of such sensors limited, increasing the costs to
cover a large area. Because the sensors attach to a central power
source, the sensor runtime is also limited, especially in remote
areas which require a battery-based power source. Furthermore, the
exposure and visibility of the cables and power and data logging
units renders the entire system vulnerable to damage, vandalism, or
theft. On a smaller scale, membranes attach over the sensor using
bolted, machined frames, which increase the sensor unit size and
cost, and often lead to mechanical failure of the sensor unit.
[0005] There is an unmet need in the art for a self-contained
dissolved gas sensor system.
[0006] There is a further unmet need in the art for a dissolved gas
sensor system capable of membrane attachment without the use of
mechanical frames.
BRIEF SUMMARY OF THE INVENTION
[0007] The present invention is a dissolved gas sensor system. The
system includes a housing having an interconnected housing body and
housing lid. A dissolved gas sensor is partially located within the
housing and partially extends through the housing lid. The
dissolved gas sensor includes a selectively permeable membrane
affixed to a dissolved gas transducer with a waterproof polymer.
This forms a membrane cavity between the selectively permeable
membrane, waterproof polymer, and dissolved gas transducer. The
membrane cavity allows the dissolved gas transducer to detect
whatever gas or gases can pass through the selectively permeable
membrane. These readings pass to a controller located within the
housing body. The controller's processor is connected to the
dissolved gas sensor and to a power supply. The controller's data
logger is connected to the dissolved gas sensor and to the
processor, while the controller's power circuit is connected to the
power supply. Using these components, the controller can receive
and process data, and store the data in a removable data storage.
The controller can also regulate overall power consumption of the
system.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWING(S)
[0008] FIG. 1 illustrates a cross-sectional view of an exemplary
embodiment of a dissolved gas measurement system.
[0009] FIG. 2 illustrates a side view of an exemplary embodiment of
the dissolved gas measurement system mounted to a base.
TERMS OF ART
[0010] As used herein, the term "data logger" refers to a device
that records data over time.
[0011] As used herein, the term "dissolved gas transducer" refers
to a device capable of measuring the amount of a specific gas or
set of gases dissolved in a solution.
[0012] As used herein, the term "processor" refers to any code
segment, circuitry or computer system, or other apparatus capable
of performing a logical, mathematical, or functional operation,
and/or transforming the type, state, value, or condition of actual
or modeled data.
[0013] As used herein, the term "selectively permeable membrane"
refers to a porous membrane which allows passage of a preselected
substance or substances while blocking all other substances.
DETAILED DESCRIPTION OF THE INVENTION
[0014] FIG. 1 illustrates a cross-sectional view of an exemplary
embodiment of dissolved gas measurement system 100. A housing 10
encases part of a dissolved gas sensor 20, along with a controller
30, a removable data storage 40, and optionally, a power supply 50,
sealing these components from potential water damage and allowing a
user to submerge the entire system 100 if necessary. A remaining
portion of dissolved gas sensor 20 protrudes from a housing lid 11.
Because housing 10 is sealed, a user must open housing 10 to remove
and replace data storage 40 and power supply 50.
[0015] Housing 10 is made from a waterproof material such as a
metal, a polymer, or a combination thereof. Housing lid 11 moveably
connects to a housing body 12, allowing a user to open housing 10
if necessary. The seam between housing lid 11 and housing body 12
is watertight due to a housing seal 13. Housing seal 13 is a
flexible, waterproof polymeric or elastomeric material. In the
exemplary embodiment, housing seal 13 is a polymer foam ring coated
with silicone grease. Optionally, at least one housing port 14
extends through housing 10 to allow the use of at least one
additional external sensor 15. Such external sensors 15 may
include, but are not limited to, a radiation sensor, such as a
photosynthetically active radiation sensor, or a pressure sensor,
such as a water pressure sensor or barometer. External sensors 15
may be used to detect external conditions, such as sunlight
reception, sensor depth, or water flow. External sensors 15 connect
to controller 30 to receive power and to transmit data.
[0016] Dissolved gas sensor 20 includes a selectively permeable
membrane 21 covering a membrane cavity 22 and sealed with a
waterproof polymer 23 to a dissolved gas transducer 24 and to
housing lid 11. A calibration tube 25 extends from membrane cavity
22 to a calibration port 26, which may be covered by a removable
port cap 27 or connected to a pressure transducer 28.
[0017] Selectively permeable membrane 21 is a porous, waterproof
polymer membrane. In the exemplary embodiment, selectively
permeable membrane 21 is a silicone membrane permeable to carbon
dioxide. Other embodiments of selectively permeable membrane 21 may
be permeable to other dissolved gasses, such as, but not limited to
oxygen, or may be formed from other materials, such as, but not
limited to polytetrafluoroethylene. Membrane cavity 22 is sized to
accommodate dissolved gas transducer 24, which forms its bottom
dimension. The top dimension of membrane cavity 22 is formed by
selectively permeable membrane 21, while the side dimension is
formed by waterproof polymer 23. Membrane cavity 22 minimizes the
quantity of whatever gas or gasses need to pass through selectively
permeable membrane 21 for dissolved gas transducer 24 to detect a
change in gas concentration.
[0018] Waterproof polymer 23 is also impermeable to the gas or
gasses measured by dissolved gas transducer 24 to ensure accurate
measurement. Furthermore, waterproof polymer 23 does not contain or
release any gasses that may interfere with readings made by
dissolved gas transducer 24. In the exemplary embodiment,
waterproof polymer 23 is a polyurethane cement. In other
embodiments, waterproof polymer 23 may be, but is not limited to,
epoxy cement or butyl rubber cement. Waterproof polymer 23
interconnects and forms a waterproof seal between selectively
permeable membrane 21, dissolved gas transducer 24, and housing lid
11. Dissolved gas transducer 24 measures levels of whatever gas or
gasses enter membrane cavity 22 through selectively permeable
membrane 21. In the exemplary embodiment, dissolved gas transducer
24 is a non-dispersive infrared transducer for measuring carbon
dioxide. Other embodiments may use different dissolved gas
transducers 24 for different gasses, such as an ultraviolet flux
transducer for measuring oxygen or an infrared transducer for
measuring methane. Dissolved gas transducer 24 is connected to
controller 30 to receive power and to process and store data.
[0019] Calibration tube 25 provides direct access to membrane
cavity 22 via calibration port 26. This allows a user to calibrate
dissolved gas transducer 24 by opening housing 10 and directly
flushing membrane cavity 22 with a calibration gas, instead of
merely placing the entire system 100 in an environment filled with
calibration gas. Not only does this eliminate the lead time for the
gas to cross selectively permeable membrane 21, it also reduces the
volume of calibration gas required to calibrate dissolved gas
transducer 24. In the exemplary embodiment, dissolved gas
transducer 24 is calibrated at 0, 200, 1,000, and 25.000 ppm of the
gas under study. After calibration, a user may close off
calibration port 26 with removable port cap 27 or connect
calibration port 26 to pressure transducer 28. Embodiments
utilizing pressure transducer 28 connect pressure transducer 28 to
controller 30 to receive power and to transmit data.
[0020] Controller 30 includes a processor 31 with a data logger 32
and a power circuit 33, a clock 34, and a temperature sensor 35.
Processor 31 is operatively connected to all sensors and to
removable data storage 40 and power supply 50. Data logger 32
receives data from all sensors and stores the data in removable
data storage 40. Power circuit 33 regulates power consumption for
system 100 using clock 34. When system 100 is in a sleep mode,
system 100 can consume 20-100 times less power than when system 100
is measuring and recording data, allowing extended data gathering
using power supply 50. Further power savings may be attained by
programming controller 30 to sleep and conserve power between
measurement intervals. Clock 34 also provides a timestamp for any
collected data.
[0021] Removable data storage 40 is a non-volatile data storage
device such as, but not limited to, an SD memory card or a USB
flash drive. In the exemplary embodiment, power supply 50 is a 7-
to 17-volt power source. In the exemplary embodiment, power supply
50 is a battery pack located inside of housing 10. In other
embodiments, power supply 50 may be a solar panel or panels located
outside of housing 10 and connected to power circuit 33 through
housing 10. This embodiment of system 100 may be used for
above-water applications.
[0022] When powered on, system 100 enters a warmup mode and warms
up dissolved gas transducer 24 for a user selected period of time.
After warm up, dissolved gas transducer 24 enters the measurement
phase and controller 30 collects data such as, but not limited to,
a raw dissolved gas transmittance signal from dissolved gas
transducer 24, estimated dissolved gas concentration data, error
checking information from dissolved gas transducer 24, a time and
date from clock 34, a power level from power supply 50, and/or a
temperature signal, at user-defined intervals, from temperature
sensor 35. In the exemplary embodiment, dissolved gas transducer 24
collects data at a frequency of 0.5 Hz. Controller 30 saves
collected data to removable data storage 40. The raw dissolved gas
transmittance signal from dissolved gas transducer 24 may be used
in later post processing for final results.
[0023] After a user-specified number of samples are recorded to
removable data storage 40, system 100 enters sleep mode. The
dissolved gas transducer 24 is powered down, and controller 30
suspends processing for user-specified intervals to minimize energy
consumption. Every interval, controller 30 wakes, checks the status
of clock 34, then determines whether to return to sleep or enter
warmup mode for another set of measurements. If system 100
encounters a detectable error, system 100 will reset itself in an
attempt to return to a proper mode of measurement operations.
[0024] After system 100 has collected a full sequence of data, a
user may retrieve system 100 and remove data storage 40. The user
may then transfer the data to an external workstation. This
external workflow can correct the data for measured or estimated
total dissolved gas pressure, barometric pressure variations, water
interference with dissolved gas transducer 24, and temperature
effects.
[0025] FIG. 2 illustrates a side view of an exemplary embodiment of
dissolved gas measurement system 100 mounted to base 200. Base 200
has sufficient mass, in the form of base weight 201, to keep system
100 submerged. In certain embodiments, base weight 201 is integral
to base 200; that is, base 200 itself has sufficient mass to keep
system 100 submerged. In the exemplary embodiment, base 200 is
further connected to at least one base anchor 202 by at least one
base connector 203 to ensure that system 100 remains in place
despite any water currents affecting system 100. Base anchor 202
may be a pipe, stake, or any other anchor known in the art that can
be embedded in the ground or a waterway bed to prevent system 100
from being displaced by water currents or any other environmental
forces. Base connector 203 may be a cable, chain, rope, or any
other connector known in the art. Other embodiments may use
environmental features or debris to keep base 200 from moving.
[0026] It will be understood that many additional changes in the
details, materials, procedures and arrangement of parts, which have
been herein described and illustrated to explain the nature of the
invention, may be made by those skilled in the art within the
principle and scope of the invention as expressed in the appended
claims. Moreover, the terms "about," "substantially" or
"approximately" as used herein may be applied to modify any
quantitative representation that could permissibly vary without
resulting in a change in the basic function to which it is
related.
[0027] It should be further understood that the drawings are not
necessarily to scale; instead, emphasis has been placed upon
illustrating the principles of the invention.
* * * * *